In recent years, multi-layered interconnection structures are being increasingly used for circuitry, because higher density and higher integration degree are required in manufacturing semiconductor devices. Under the circumstances, embedding techniques for electrical connection between layers have become important, e.g., at contact holes used as connections between an underlying semiconductor device and upper interconnection layers, and at via-holes used as connections between upper and lower interconnection layers. Further, in order to meat high dielectric constant materials, such as Ta2O5 and HfO2, used as capacitor materials in, e.g., DRAM memory sections, techniques for forming an upper electrode thereon with higher coverage have also become important, along with the increase in integration degree.
Recently, TiN films are used as barrier layers for metal filled in contact holes and via-holes, and as upper electrodes in capacitors, as described above.
Conventionally, PVD is utilized in methods for forming TiN films of this kind. However, in recent years, along with the increase in miniaturization and integration degree of devices, CVD is sometime utilized, because CVD can be expected to provide a film with better quality and higher coverage.
Where a TiN film is formed by CVD, film formation is performed at a temperature of 500 to 600° C. while TiCl4 used as a reactive gas and NH3 or MMH (monomethylhydrazine) used as a nitrogen-containing reducing gas are supplied. Further, in order to prevent the underlayer from being affected by film formation, a technique has been proposed of alternately repeating a step of supplying a reactive gas and a reducing gas and a step of supplying only the reducing gas, thereby allowing the film formation to be performed at a low temperature of about 450° C. (Patent Document 1).
However, high dielectric constant materials, such as Ta2O5 and HfO2, are sensitive to temperature. In addition, where a TiN film is formed thereon as an upper electrode, it is necessary to perform the film formation at a low temperature of less than 450° C. so as to prevent the underlayer from suffering thermal damage. In this respect, if the technique disclosed in Patent Document 1 is used to perform practical film formation at such a low temperature, abnormal growth occurs during formation of metal nitride films and causes problems, such as degradation in film quality and increase in resistivity.
Further, there is a case where NiSi is used as a contact material, although NiSi is low in heat resistance. Accordingly, where a metal nitride film is formed on an NiSi underlayer, it is preferable to perform the film formation at a low temperature of 450° C. or less.
Furthermore, in recent years, along with the increase in density and integration degree being required, it has become necessary to improve step coverage.
Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2003-77864